Inductive limiting device for alternating currents



1,642,343 p 1927' F. RAIMONDI INDUCTIVE LIMITING DEVICE FOR ALTERNATING CURRENTS Filed A112. 11, 1925 Patented Sept. 13, 1927.

are smite-s 1,642,343 PATENT oil-r cer rnenonsoo .nnmonm, anner, i'lALY.

mnnczrxvn LIMITING nnvron ron ALTEBNATING ounnnu'rs.

Application filed August 11, 1925, Serial N0.'49,674, and in Germany August 26, 1924.

The apparatus, subject of the present inventiomacts in. an inductive manner in the consumption circuit; It is characterized by at least one exciter windin which encloses a magnetic .core, on vvhich' t ere is arranged a vcorresponding number of armature windings either in circuit with a negligible resistance, or connected in series or parallel with the correspondingexciter Winding and m oppositely wound. The saidarmature'wind- "in :form aunovable complex capable of being connected up with the magnetic-memhers. 'Thes ma1gneticmembers are so formed and arranged at when "they become active I5 by current increase'they form abaft'themoV- able armatures an outlet or shunt romhe fliix traversing "the core, as soon --as the-entire system be ins to -be 'infiueneednmder the action of't e attraction ofthe-coreon the magnetic organs,which assist the electromagnetic repu'lsion which develops between the exciter rand "armature windings; This magnetic outlet or shunt, then, is for' the purpose of annulling "the compensating -.action which is exercised by the armature windings on the self-induction resistance inherent in the 'exci ter windings. comprehensively this apparatus can be used in all cases whereby their vpeculiar feature, electric current is automatical=ly.r.prevented from exceeding aprevious'ly determined limit in that, by their automatic action, they reduce the current 'to a value previously arbitrarily determined and in :that they automatically return to their normal position as soon as the cause whichproduced an extraordinary increase of i the .cnrrenthas ceased toexist.

The-'apparatuscoming within the scope of the :present invention can the smade in very different constructive forms, accordingwto the nature of the chosen .c ore, according .to the number of windings chosen, andacoording to the nature of the currents to be hunted, which maybe single phase ornrultiphase.

In the accompanying. :drawing there ,is shown in ran example "of a constructional form, a diagram relating :to apparatus for three-phase currents, whichis to replace, the ordinary motor starters of this kind.

The apparatus is connected upbetween the three-phase motor Mend the circuit breaker Sfbyineans.o-fwhich the device can be connected up :to the three feedersI, Hand III.

LThe apparatus itself composed of the three windings '1, 2 and a?) whidh are connested in series with :the motor :and enclose I V the three arms 4,;5 vand 6, of'ia magnetic core, which is connected by the two transverse parts 7 and '7. The armature Wind.- i-ngs of a smallielectric resistance, which are closed in short .circuit,;a1re here represented by the triple ring 8 and 8. Thelatt-erican be considered as consisting of three rings rigidly connected withone another, each one of which encloses :one of the arms of the core. The parts, which serve for the. mag- :netic conduction through which, the magnetic "flux flows from :one of the arms .4, ;5 or :6, to

the other, witlrouttransversing the .crosspiece 7, are formed by two parts 9 and 9' of magnetizable metal :in -the :shape 7 of tiles. The interior :suriace of 'theselparts is so :formed that it fitszinto the :Eorm of the interior (opening of the rings, into which the parts are inserted, while their back so formed-that the pieces can :roll off on the side surfaces of the-core arms, against which the pieces bear. Each piece hasitwo lateral :lugszzor plates which embrace the arms-0i "the core and each one of which has .a series or indentations 10 dndlO, which can sucacessively engage with the pins 11 and 11".

These pinszarearranged as a ladder on the sides sof the arms of the core. The indenta- "tions 10 and 10 cooperate with theparts 9 andw9 in their movement which they effect under the control of thering 8 and 8.

In this arrangement, as soon as the electromagnetic repulsion ointhe windings1,2and

3'on the -triple ringfi an'd 8 has reached a "sufiicient ivalue to compensate its weight and as soon as the magnetic attraction of the 5 on the parts 19 and 9' has become suffiiclent'ly strong'(which is the case as soon as "the current-strength absorbed by the motor extent the magnetic shuntibetween the arms of the 0116, which practically stops every compensating action of the ring on the self induction resistance of the windings .1, '2

Let us assume that motor M is to be start red. For this it suiiices 'to'clos-e the circuit b-IBQJkGI'VIS. The current, accordingly, has

the tendency to enter with an extraordinarily high intensity,. since the motor develops no counter'electro magnetic force, .as it is resistance of the windings 152 and 3becomes effective, and consequently the intensity of the supply current is reduced to the desired Value, that is, the value which suffices for the starting. As soon as the motor has reached a speed sufficient to lower thecurrent intensity, which normal corresponds to-the motor,.the apparatus will: take again its position of rest, in which the impedance of'the windings 1, 2 and 3 can be neglected 11 account of the compensating action of the ring Sand 8'.

The position of the triple ring Sand .8 and-the parts 9 and 9 corresponding to the starting of the motor to which-the apparatus is applied is that'shown on the drawing in'dotted lines. 'The 'position of the elements corresponding to the running of the motor is that shown in full lines.

More specifically when the apparatus is traversed by the normal excitation current thering 88 is not yet balanced by the. repulsive electrodynamic action of the current flowing through the'windings l2 3; the induced current flowing through this ring, which reduces the impedance set up by. the

windings, also limits'the magnetizingof the core, and the-parts. 9-9 remain in equili- 'brium because they cannot yet overcome the dead weight of the ring on account of their great distance from the middle arm which attracts them and of the feebleness of the active magnetism. WVhen the apparatus is traversed by thepredetermined maximum current, the ring 8-8 tends to rise under the pushof the aforesaid electrodynamic action and the magnetism of the coreis reinforced bythe increase of the circulating current; the parts 9--9' can then enter into action because they no longer have to over- "come any weight and they yield to amagnetic attraction which has become sufficient.

As soon as the apparatus is started, the

magnetic attraction of the middle arm on the parts 9-9 starts to increase rapidly on account of the progressive approach of the parts 9-9 to the middle arm and of the increase of magnetizationconsequent upon the separation of the ring; these-- pieces then move the'said ring 8-8 sharply upward, whereas they roll against the flanks of/the external arms in the direction necessary to .permit their approach toward the middle arm. The structural embodimentrepresented tends to facilitate and regulate tlliSTOlling movement, since the parts 99 are shaped like c-rescents and engage the flanks of the arms and the internal flanks of the multiple ring 88.

The apparatus thus acts as an automatic Nevertheless, it can play the part.

starter. of .a safety device, since as soon as, for any "cut out of the circuit by means of the circuit breaker S, the apparatus wilrprevent any damage in that it automatically acts as a starter v Y I t is apparent that this apparatus canbe used for single-phase currents. For this it suflices to disconnect the two windings 1 and 3 and the respective armaturesand to retain winding 2 and its armature. winding 2 would be connected to a singlephase. l 1

Any other kind of core may also be used. Thenecessary modifications for the windings and for the parts effecting the magnetic short circuit may be chosen to fit the conditions and that in such manner as preferred by three arms; a metal cross piece for each of the ends ,of the arms; an exciter winding foreach arm of said .core; a triple ring surrounding the arms of the core forming areaction winding; a plurality of pinson the two outer arms ofthecore; and a pair of metal. parts guided and cooperating with the pinson the outerarms of the core for effecting a magnetic shunt for the core.

2. An inductive electro-magnetic limiting device comprising'a magnetic core; an exciter winding forsa-id core; adjusting means for effecting a magnetic shunt-for the core; and means forming-a reaction winding and adapted to be adjusted by said adjusting means. j

3. Aninductive eleotro-magnetic limiting device comprising a magnetic core; an exciter winding for said core; adjusting means for effecting a magnetic shunt for the core; and; a movable ring surrounding'said core forming a reaction winding and adapted to be adjustedby said means.

4. An inductive electro-magnetic limiting device comprising a magnetiocore; an excite'r winding for said core; adjusting means for effecting a magnetic shunt for the core; and a ring surrounding said core comprising a plurality of windings forming a reaction winding and adapted to. be adjustedby said means.

5. An inductive electro-magnetic limiting device comprising a. magnetic core; an exciter winding for saidjcore; apair of metal parts on the core for effecting a magnetic shunt for the core; and a ring surrounding said core, forming a reaction Winding and adapted to be adjusted; by said pair of metal parts.

In this case,

6. An inductive electro-magnetic limiting device comprising a magnetic core having three arms; an exciter Winding for each arm of said core; adjusting means for eifecting a magnetic shunt for the core; and a triple ring surrounding the arms of the core forming a reaction Winding and adapted to be adjusted by said means.

7 An inductive electro-magnetic limiting device comprising a magnetic core having three arms; an exciter winding for each arm of said core; a pair of metal parts on the core for effecting a magnetic shunt for the .core; and a triple ring surrounding the arms of the core forming a reaction Winding and adapted to be adjusted by said means.

8. An inductive electro-magnetic limitmg device comprising a magnetic core having three arms; a metal crosspiece for each of the ends of the arms; an exciter Winding for each arm of said core; adjusting means for effecting a magnetic shunt for the core; and a triple ring surrounding the arms of the core forming a reaction Winding and adapted to be adjusted by said means.

In testimony whereof I affix my signature.

FRANCESCO RAIMONDI. 

